Why does my computer screen bounce up and down sometimes?

Why does my computer screen bounce up and down sometimes ive done virus scans and adaware nothing found?

• Answer:

  If you have a CRT monitor - the old tube type that look like a small TV, then it is a natural function called degaussing. If it happens more than once a day, or happens while you are using the computer, check to see that your speakers are 6" or more from the monitor. If that doesn't help, your monitor is probably getting close to failing. If you have a flat-panel LCD monitor, it is caused by the monitor re-adjusting to the video signal. Most low-quality monitors do this frequently, especially Acer and AOpen brands. My Sony never does it, but I have seen several cheap models do it constantly - every 5 minutes or so. You may be able to get around it by adjusting the settings manually for the monitor picture placement, or just disabling automatic adjustments.